Systems and methods for the conditioning of cerebrospinal fluid

ABSTRACT

Systems and methods for treating biologic fluids are disclosed. Some disclosed embodiments may be used to filter cerebrospinal fluid (CSF) from a human or animal subject, heat CSF to a target temperature, cool CSF to a target temperature, apply light treatment to CSF, separate cells via their dielectric properties, apply spiral and/or centrifugal separation, introduce additives to target particles, and/or apply combinations thereof. The method may include the steps of withdrawing fluid comprising CSF, treating the fluid, and returning a portion of the treated fluid to the subject. During operation of the system, various parameters may be modified, such as flow rate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119 of the earlierfiling date of U.S. Provisional Patent Application No. 62/263,305, filedDec. 4, 2015, entitled “Systems and Methods for the Conditioning ofCerebrospinal fluid,” which is hereby fully incorporated by referencefor any and all purposes as if fully set forth herein in its entirety.

Embodiments described in this application may be used in combination orconjunction with the subject matter described in one or more of thefollowing, each of which is hereby fully incorporated by reference forany and all purposes as if set forth herein in their entireties:

U.S. Pat. No. 8,435,204, entitled “Cerebrospinal Fluid PurificationSystem,” which issued May 7, 2013, which is the U.S. National Phaseentry of International Patent Application Number PCT/US2007/080834,filed Oct. 9, 2007, which claims the benefit of U.S. ProvisionalApplication No. 60/828,745, filed on Oct. 9, 2006;

U.S. patent application Ser. No. 14/743,652, filed Jun. 18, 2015,entitled “Devices and Systems for Access and Navigation of CerebrospinalFluid Space,” which claims the benefit of U.S. Provisional ApplicationNo. 62/038,998, filed on Aug. 19, 2014;

U.S. patent application Ser. No. 13/801,215, filed Mar. 13, 2013,entitled “Cerebrospinal Fluid Purification System,” which is acontinuation of U.S. patent application Ser. No. 12/444,581, filed Jul.1, 2010, which issued as U.S. Pat. No. 8,435,204 and is the U.S.National Phase entry of International Patent Application NumberPCT/US2007/080834, filed Oct. 9, 2007, which claims the benefit of U.S.Provisional Application No. 60/828,745, filed on Oct. 9, 2006; and

U.S. patent application Ser. No. 15/287,174, filed Oct. 6, 2016,entitled “Devices and Methods for Providing Focal Cooling to the Brainand Spinal Cord,” which claims the benefit of U.S. Provisional PatentApplication No. 62/237,867, filed Oct. 6, 2015.”

BACKGROUND

Cerebrospinal fluid (CSF) is a generally clear, colorless fluid that isproduced in the ventricles, specifically the choroid plexuses, in thebrain. The choroid plexus produces approximately 500 milliliters of CSFdaily to accommodate flushing or recycling of CSF to remove toxins andmetabolites, which happens several times per day. From the choroidplexus, CSF flows slowly through a channel (canal) into the spinalcolumn, and then into the body. CSF is found in the space between thepia mater and the arachnoid mater, known as the subarachnoid space. CSFis also found in and around the ventricular system in the brain, whichis continuous with the central canal of the spinal cord. It may bedesirable to remove, condition, and return CSF to treat various medicalconditions. The present disclosure sets forth treatment modalities,methodologies, and therapies in this context.

The information included in this Background section of thespecification, including any references cited herein and any descriptionor discussion thereof, is included for technical reference purposes onlyand is not to be regarded subject matter by which the scope of theinvention is to be bound.

SUMMARY

In some embodiments, the performance of CSF-treatment systems may beimproved by various treatments of CSF, including heating the CSF to atarget temperature, cooling the CSF to a target temperature, increasingCSF flow rate, applying light treatment to the CSF, applying an osmoticgradient to lyse cells, separating cells via their dielectricproperties, applying spiral and/or centrifugal separation, bindingadditives to target particles within the CSF, other treatmenttechniques, or combinations of these.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a system for treating biologic fluids according tosome embodiments, with solid arrows indicating an example fluid flowdirection.

FIG. 2 illustrates fluid being withdrawn from and returned to atreatment site, according to some embodiments.

FIG. 3 illustrates fluid being withdrawn from and returned to atreatment site, according to some embodiments.

FIG. 4 illustrates a block diagram of a treatment system, according tosome embodiments, with solid arrows indicating an example fluid flowpath and dashed arrows indicating an example flow path for signals orinformation.

FIG. 5 illustrates a filter portion of a treatment system, according tosome embodiments.

FIG. 6 illustrates a flow diagram for a method for using a treatmentsystem for treating biologic fluids according to some embodiments.

FIG. 7 illustrates systems and methods for treating CSF by altering thetemperature of the CSF and filtering the CSF according to someembodiments

FIG. 8 illustrates systems and methods for treating CSF with ultravioletlight according to some embodiments.

FIG. 9 illustrates an embodiment of a treatment system having a valveand a feedback path to increase fluid flow rate across a filteraccording to some embodiments.

FIG. 10 illustrates a dielectrophoresis system which uses electrodes tocreate an electric field to direct particles towards particular pathsaccording to some embodiments.

FIG. 11 illustrates a polynomial channel path according to someembodiments.

FIG. 12 illustrates a polynomial channel path according to someembodiments.

FIG. 13 illustrates a dielectrophoresis system having 3D cylindricalelectrodes according to some embodiments.

FIG. 14 illustrates a dielectrophoresis system having 3D castellatedelectrodes according to some embodiments.

FIG. 15 illustrates a dielectrophoresis system having a 3D semi-circleelectrode design according to some embodiments.

FIG. 16 illustrates systems and methods for using spiral or centrifugalseparation according to some embodiments.

FIG. 17 illustrates a cross section of a path of a spiral or centrifugalseparation system according to some embodiments.

DETAILED DESCRIPTION

Disclosed embodiments generally relate to improved systems and methodsfor treating biologic fluids of a human or animal subject. In someembodiments, a filter, such as a tangential flow filter (TFF), may beused to separate cerebrospinal fluid (CSF) into permeate and retentate.The permeate may be returned to the subject. In some embodiments, theretentate may subjected to additional conditioning. For example, it maybe filtered again, such as through one or more additional tangentialflow filters or other methods of filtering. During operation of thesystem, various parameters may be modified, such as flow rate andpressure. Certain systems and methods described herein may be combinedwith other systems and methods for conditioning, removing, or otherwiseprocessing biological materials, such as those discussed in U.S. Pat.No. 8,435,204. In some embodiments, treating the biologic fluids mayinclude heating CSF to a target temperature, cooling CSF to a targettemperature, applying light treatment to CSF, separating cells via theirdielectric properties, applying spiral and/or centrifugal separation,introducing additives to the CSF, applying combinations thereof, orother techniques

FIG. 1 illustrates a system 100 for the treatment of biologic fluidsaccording to certain embodiments, including a treatment system 102, anintake 104, a retentate outlet 106, a permeate outlet 108, a vessel 110,a treatment site 112, and tubing 114. The arrows represent an exampledirection that fluid may take through the system.

In certain embodiments, the treatment system 102 is a device orcombination of devices that is configured to filter, concentrate,dialyze, separate, or otherwise treat or condition the fluid, itscontents, or both. In some embodiments, the treatment system 102 maytreat the subject by modifying the fluid. For example, the treatmentsystem 102 may treat a portion of the subject's spinal cord or brain bycooling the withdrawn fluid and returning the cooled fluid to causelocal cooling. The treatment system 102 may include a tangential flowfiltration system (for example, as shown and described in relation toFIG. 5) or other system configured to filter fluid. In some embodiments,the treatment system 102 receives the fluid through an intake 104 andreturns the fluid through one or more outlets. For example, in certainembodiments, the treatment system 102 receives the fluid through theintake 104 and separates the fluid into retentate and permeate. Theretentate exits the treatment system 102 through a retentate outlet 106,and the permeate exits the treatment system 102 through a permeateoutlet 108.

The intake 104 may be a port through which fluid enters the treatmentsystem 102. The retentate outlet 106 may be an outlet through whichretentate exits the treatment system 102. The permeate outlet 108 may bean outlet through which permeate exists the treatment system 102.

The intake 104, retentate outlet 106, and permeate outlet 108 may be anykind of ports through which material or fluid may flow. These componentsmay be configured to be in fluid connection by tubing 114. Thecomponents 104, 106, 108, 114 may include various fittings to facilitatethe connection, including but not limited to compression fittings, flarefittings, bite fittings, quick connection fittings, Luer-type fittings,threaded fittings, and other components configured to enable fluid orother connection between two or more components. In addition tofittings, the components 104, 106, 108, 114 also may include variouselements to facilitate use of the system 100, including but not limitedto various valves, flow regulators, adapters, converters, stopcocks,reducers, and other elements.

In certain embodiments, there may be one or more outlets, such as one ormore permeate outlets 108 and/or retentate outlets 106. For example, thesystem 100 illustrated in FIG. 1 includes a treatment system 102 havingtwo permeate outlets 108. This configuration may facilitate the use ofdifferent treatment systems within a treatment system 102. For example,the treatment system 102 may include multiple filtration components,each with their own individual outlets. In some embodiments, thetreatment system 102 does not separate the fluid into permeate andretentate, and the treatment system 102 does not have permeate andretentate outlets.

The vessel 110 may be a container for storing fluid. For example, fluidleaving the treatment system 102 may be deposited in the vessel 110. Thefluid deposited in the vessel 110 may be held for storage, wastedisposal, processing, testing, or other uses. The vessel 110 may also bea reservoir for subsequent treatment, for example, through the sametreatment system 102 or a different treatment system 102. This fluid mayor may not be combined with previously filtered fluid.

The treatment site 112 may contain a particular fluid to be treated. Insome embodiments, the treatment site 112 may be an anatomical entity orlocation within a human or animal subject, such as a chamber orCSF-containing space or a blood vessel. The treatment site 112 may bethe source of the fluid, the destination of the fluid, or both. Forexample, the system 100 may remove or receive a volume of fluid from thetreatment site 112, perform treatment, and return a portion of theprocessed and/or treated fluid to the treatment site 112.

The various components of the system 100 may be connected through tubing114. For instance, in certain embodiments, there may be a length of thetubing 114 placing the treatment site 112 in fluid connection with theintake 104. The permeate outlet 108 may be in fluid connection with thetreatment site 112 via a length of the tubing 114. The retentate outlet106 may be in fluid connection with the vessel 110 via a length of thetubing 114. The tubing 114 may be any kind of system for transporting orcontaining fluid. While the connections within the system 100 are shownas being direct, the connections need not be. The various portions ofthe system 100 may be connected through combinations of connections andvarious tubing 114. In certain embodiments, the tubing 114 and otherportions of the system 100 may be filled with priming fluid (e.g.,saline). Longer lengths of tubing 114 may correspondingly comprise alarger amount of priming fluid; however, in some embodiments, largeramounts of priming fluid may result in an undesirable amount of dilutionof “natural” or endogenous fluid, such as CSF. Accordingly, in someembodiments, the tubing 114 may be selected to minimize the volume ofpriming fluid needed, while still having the system be practicallyuseful (e.g., enough tubing to enable the system 100 to be used at asubject's bedside). Depending on the subject and the treatment site 112,the tolerance for removal or dilution of fluid may vary, and the system100 may be scaled accordingly. For example, the parameters of the system100 may be changed to scale to suit subjects ranging from a mouse to ahuman or larger mammals.

In some embodiments, the tubing 114 may have a port 124 configured toprovide access to the fluid traveling within the tubing 114. Asillustrated in FIG. 1, there is a port 124 between the permeate outlet108 and the treatment site 112. This port 124 may be configured for theintroduction of additives, such as therapeutic agents, artificial fluid(such as artificial CSF), and/or other additives. The port 124 may alsobe configured for the removal of fluid for testing or other purposes.For example, in certain embodiments, fluid returning to the treatmentsite 112 may be removed and tested for particular characteristics orparameters. In certain embodiments, tubing 114 that links the treatmentsite 112 to the intake 104 may include a port 124. This port 124 mayalso be used for the introduction of additives and/or the removal offluid. In some embodiments, instead of or in addition to a port 124located on the tubing 114, there may also be a port 122 located on thetreatment system 102 itself. This port 122 may be used to access thefluid within the treatment system 102 at various points during treatmentfor various purposes. For example, like the port 124, the port 122 maybe used to introduce additives to the system 100 or remove fluidtherefrom. In some embodiments, the ports 122, 124 may be used to linkthe system 100 with other systems.

FIG. 2 illustrates a system and method for withdrawing a fluid 202 fromand returning fluid to the treatment site 112, according to someembodiments. The connection between the system 100 and anatomicalstructures (such as the treatment site 112) may be made in a variety ofways. For example, if the treatment site 112 is an anatomical locationwithin a subject, as shown in FIG. 2, the connection with the treatmentsite 112 may be made through one or more catheters inserted intoparticular anatomical locations. For example, the catheter may be amulti-lumen catheter inserted through a single opening in the subject toaccess the anatomical location or may be two catheters inserted at twodifferent, but connected anatomical locations. In some embodiments, theconnection may be made via an external ventricular drain system. Forexample, the tip of a catheter may be placed in a lateral ventricle ofthe brain.

As a specific example, the some embodiments shown in FIG. 2 include aportion of a subject's spine 200, including vertebrae 201, carrying afluid 202 (for example, a fluid comprising CSF), and a multi-lumencatheter 204. The multi-lumen catheter 204 may comprise a first port 206and a second port 208 that place the treatment site 112 in fluidconnection with tubing 114. As illustrated, a first volume of the fluid202 enters the multi-lumen catheter 204 through the first port 206 andis passed through into a portion of the tubing 114 (for example, aportion of tubing 114 leading to the intake 104). A second volume offluid 202 enters the multi-lumen catheter 204 from a portion of thetubing 114 (for example, a portion of tubing 114 coming from thepermeate outlet 108) and exits the multi-lumen catheter 204 through thesecond port 208.

The catheter 204 may, but need not, also include ports to place one ormore lumens in fluid connection with the fluid 144 of the treatment site112. The catheter 204 may be generally configured to be flexible,navigable, and atraumatic. The catheter 204 may enable sensing oftemperature, intracranial pressure, and/or other parameters. The size ofthe catheter 204 may be approximately greater than or equal to 6 Frenchand approximately 20 cm to approximately 120 cm to enable attachment toremote tubing (e.g. the tubing 104), a console (e.g., the treatment unit106), or other units; however, other sizes may be used. In someembodiments, the catheter size may be approximately 5 French. Otherdiameters and lengths may be used, as desired.

FIG. 3 illustrates a system and method for withdrawing fluid from andreturning fluid to the treatment site 112, according to someembodiments. In this particular example, tubing 114 and a mutli-lumencatheter 204 are placed in fluid connection with the ventricles of asubject's brain 210. This configuration may be similar to or describedas an external ventricular drain.

Although FIGS. 2 and 3 illustrate accessing CSF in a portion of thespine 200 and a portion of the brain 210, respectively, the embodimentsdisclosed herein need not be limited to those regions or that fluid andmay be used with other locations and fluids. For example, one or moresingle-lumen catheters may be used to transport the fluid 202. Asanother example, the anatomical location may be a blood vessel and thefluid may be blood.

FIG. 4 illustrates a block diagram of a treatment system 102 accordingto certain embodiments, with solid arrows indicating an example flowpath for fluids and materials and dashed arrows indicating an exampleflow path for signals and information. FIG. 4 illustrates the intake104, the retentate outlet 106, the permeate outlet 108, a pump 222, anair trap 223, a sensor 224, a treatment unit 226, a processing unit 228,and an interface 230. Various components of the system may be selectedto be fluid-contacting components or non-fluid-contacting components.Whether a component contacts the fluid may affect whether the componentis disposable and the ease with which the component may be reused.

The pump 222 may be any device for inducing fluid flow through one ormore portions of the treatment system 102. In certain embodiments, thepump 222 may be a peristaltic pump, which may reduce the need forsterilization of complex pump components; however, other types of pumpsmay be used. The operation of the pump 222 may be controlled bymodifying the operating parameters of the pump 222. This may enable theflow rate, pressure, and/or other parameters of the pump 222 to bechanged. The pump 222 may also be used to withdraw the fluid from thetreatment site 112.

The air trap 223 can be used to facilitate priming the treatment system102 and can be used to remove air bubbles from the system 102 to improveaccuracy of the sensor 224. The air trap 223 can include a hydrophobicair vent.

The sensor 224 may be a device for generating and/or receivinginformation, including but not limited to one or more of characteristicsof the fluid withdrawn from the treatment site 112, before, after,and/or during filtration, including but not limited to temperature;pressure; the ratio of permeate volume to retentate volume; the fluidflow rate to and/or from the treatment site 112; the amount ofcontaminants or other materials in the fluid; the fluid flow returnrate; the filter efficiency; filter status (for example, whether thefilters are clogged or otherwise running inefficiently); and otherparameters or characteristics. While the sensor 224 is shown within thetreatment system 102, one or more sensors 224 may be located elsewherein the system 100 and/or cooperate with other locations. The sensor 224may convert the data into computer- and/or human-readablerepresentations for processing. While a single sensor is shown withinthe system, it will be understood that there need not be only as singlesensor. Any suitable number or arrangement of sensors may be used fortaking one or more readings throughout the system.

In some embodiments, the sensor 224 may be selected to or optimized foruse with flow rates of approximately 0 to approximately 1200 millilitersper hour, volumes of approximately 100 to approximately 125 cubiccentimeters, and pressures of approximately 0 to approximately 20 mmHg.These measurement ranges may be encountered in the system, such as inthe flow rate, volume, and pressure of CSF or a heat exchange fluid. Insome embodiments, the flow sensor may be accurate within a range ofbetween approximately 0 to approximately 2400 milliliters per hour, thepressure sensor may have an effective operating range of betweenapproximately −50 mmHg and approximately 300 mmHg. In some embodiments,sensor 224 may have a response time of approximately 20 ms. In someembodiments, the sensor 224 may be a temperature sensor configured tohave an accuracy of +/−0.5° C. between approximately 4° C. andapproximately 70° C. Suitable sensors may include flow sensors providedby SENSIRION of Switzerland, pressure sensors by UTAH MEDICAL ofMidvale, Utah, and temperature sensors by SCILOG of Madison, Wis.

The treatment unit 226 may be configured to treat fluid and may be oneor more components of the treatment system 102. For example, in someembodiments, the treatment unit may be a device for separating a firstportion of materials and/or fluid from a second portion of materialsand/or fluid. The design and type of the treatment unit 226 may varydepending on the type of fluid and the desired treatment results. Forexample, the treatment unit 226 may include a tangential flow filterconfigured to separate the fluid into permeate and retentate (see, forexample, FIG. 5), with the retentate flowing to the retentate outlet 106and the permeate flowing to the permeate outlet 108. For example,various combinations of filters may be used to achieve different kindsof filtration. For example, the filters may include filters of variouspore sizes and different attributes. For example, filtering schemes mayinclude ultrafiltration, microfiltration, macrofiltration and othersized filters that have various porosities. Combinations of filters mayinclude dead end filtration, cone filters, depth filtration, tangentialflow filtration, affinity filtration, centrifugal filtration, vacuumfiltration, other configurations, and/or combinations thereof. Multipletreatment systems may be used to continually re-filter retentate toyield a higher volume of permeate that may be returned to the treatmentsite 112. In an embodiment, the filter may be configured to filtercytokines. See U.S. Pat. No. 8,435,204, previously incorporated byreference. Examples of cytokines and other proteins that may be filteredmay include, but need to be limited to, EGF, Eotaxin, E-selectin, fasligand, FGF2, Flt3 lig, fractalkine, G-CSF, GM-CSF, GRO, ICAM, IFNa2,IFNg, IL10, IL12p40, IL12p70, IL13, IL15, IL17, IL1a, IL1b, IL1ra, IL2,IL3, IL4, IL5, IL6, IL7, IL8, IL9, integrins, IP10, L-selectin, MCP1,MCP3, MDC, MIP1a, MIP1b, PDGF-AA, PDGF-AAAB, P-selectin, RANTES, sCD40L,sIL2R, TGFa, TNF, TNFb, VCAM, VEGF, and others. In some embodiments, thefilter may be configured to capture and absorb cytokines in the about 10to about 50 kDa range where most cytokines reside.

In some embodiments, the treatment unit 226 may include multipledifferent treatment components, including but not limited to filters,components configured to increase the performance of filters, unitsconfigured to increase the flow rate of the fluid within the treatmentsystem 102, units configured to heat the fluid, units configured to coolthe fluid, units configured to apply light treatment to the fluid, unitsconfigured to separate components of the fluid based on their dielectricproperties, units configured to apply spiral separation, unitsconfigured to apply centrifugal separation, units configured tointroduce additives to the fluid, units configured to target particularcomponents of the fluid, other components, and/or combinations thereof.Some embodiments may be configured to mechanically vibrate filters inorder to reduce filter clogging, improve flow, and improve reliability.Some embodiments may include an inline air trap. The inclusion of an airtrap may increase performance by, for example, removing air bubbles thatmay otherwise be detrimental to the system by causing erroneous sensorreadings and filter airlocks.

The processing unit 228 may be a device configured to control theoperation of the treatment system 102, for example by sending signals tothe pump 222, sensor 224, and/or treatment unit 226. In someembodiments, the signals are sent in response to receiving input fromthe interface 210. In certain embodiments, the processing unit 228 mayprocess information, such as data received from the sensor 224 and/orthe interface 210 and make decisions based on the information. Incertain embodiments, the processing unit 228 may itself make decisionsbased on the information. For example, the processing unit 228 mayinclude a processor and memory for running instructions configured toreceive input, make decisions, and provide output.

The interface 230 may be a device or system of devices configured toreceive input and/or provide output. In certain embodiments, theinterface 230 is a keyboard, touchpad, subject monitoring device, and/orother device configured to receive input. For example, a healthcareprofessional may use the interface 230 to start or stop the system 100and to modify system parameters, such as the absolute duration of theprocedure, pump speed, and other parameters. The interface 230 may alsoinclude a display, speaker, or other device for sending user-detectablesignals. In some embodiments, the interface 230 may comprise a networkinterface configured to send communications to other devices. Forexample, the interface 230 may enable the treatment system 102 tocommunicate with other treatment systems, flow control devices, aserver, and/or other devices.

FIG. 5 illustrates a segment of the treatment unit 226 according to someembodiments, including a first section 256, a membrane 258, and a secondsection 260, with arrows indicating flow direction. As shown in FIG. 5,the treatment unit 226 is configured to include a tangential flowfilter. In this configuration, the fluid 202 may enter this portion ofthe treatment unit 206 and pass through the first section 256. While thefluid 262 travels through the first section 256, the fluid 262 mayencounter the membrane 258. A particular pressure, flow rate, or otherenvironmental condition within the first section 256 and/or secondsection 260 may draw or otherwise encourage fluid to contact themembrane 258. The environmental condition may be created by, forexample, the shape, size, or configuration of the treatment unit 226.The environment may also be created as a result of the pump 222 or otherfeature of the treatment system 102 or system 100. As a result, certaincomponents of the fluid 262 (for example, components 252) may passthrough an aperture of the membrane 258 to the second section 260.However, certain other components (for example, contaminants 254) may beimproperly sized (for example, the certain other components are toolarge) to pass through the membrane 258 and instead remain within thefirst section 256. The fluid 262 that passes through the membrane 258into the second section 260 may be described as permeate and may passthrough to the permeate outlet 108.

As a specific example, the fluid 262 may be CSF having particulardesirable components 252. The CSF may also contain contaminants 254,such as blood cells, blood cell fragments, hemolysis components,neutrophils, eosinophils, inflammatory cells, proteins, misfoldedproteins, cytokines, bacteria, fungi, viruses, small and largemolecules, oligomers (such as Aβ oligomers, tau oligomers, α-synucleinoligomers, and Huntingtin oligomers), antibodies (such as anti-myelinantibodies), enzymes, mutated enzymes (such as mutations to SOD1),and/or other substances. The contaminants 254 may, but need not, includematerials or matter that are present in CSF normally (e.g. a cytokinethat is present in CSF normally but is present in an elevated orotherwise undesirable amount). One or more of the contaminants 254 maybe associated with or suspected to be associated with one or morediseases or conditions. For example, the contaminants 254 may beassociated with one or more of Alzheimer's disease, Parkinson's disease,multiple sclerosis, Huntington's disease, amyotrophic lateral sclerosis,for instance, as described in U.S. application Ser. No. 13/801,215,which was previously incorporated by reference. The treatment unit 226may be used to separate the contaminants 254 from the fluid and/ordesirable components 252 of the CSF. For instance, a membrane 258 may besized or otherwise configured to allow CSF to flow through the membrane258 while substantially preventing contaminants 254 from passing throughthe membrane 258.

FIG. 6 illustrates a method 400 for using a treatment system fortreating biologic fluids, including the steps of starting the process402, withdrawing a volume of fluid 404, treating the volume of fluid406, measuring characteristics 408, returning a volume of fluid 410,determining 412, updating parameters 414, and ending the process 416.The method may be utilized with certain embodiments, including system100. While the method will be described with reference to system 100, aperson of skill in the art would be able to modify the steps to be usedwith other systems, including systems having a multiple treatmentsystems.

While the method is described as being performed on a particular volumeof fluid, the system may operate on a continuous flow of fluid. That is,the system 100 need not necessarily withdraw a volume of fluid, wait forthe volume to be processed and returned, and then withdraw anothervolume of fluid. The method may follow a continuous process. Similarly,while FIG. 6 appears to illustrate a series of consecutive steps, thesteps of the described method may occur concurrently. For example, thesystem 100 may concurrently perform some or all of the steps illustratedin FIG. 6. For instance, the system 100 may concurrently withdraw andreturn fluid.

The method 400 may begin at start 402. This step 402 may includeactivating one or more components of the system 100. This step 402 mayalso include or follow various preparation steps. Such steps may includeinstalling treatment components, selecting and preparing the treatmentsite 112, installing tubing 114, calibrating components, primingcomponents of the system 100, and other steps.

The installing treatment components step may include selectingparticular treatment components based on desired outcomes, theparticular treatment site 112, fluid, or other considerations. Forexample, if the method 400 is being used on a subject suffering from acerebral vasospasm, the goal of the procedure may be to filter bloodbreakdown products from the subject's CSF. This would make the treatmentsite 112 a lumen carrying CSF, the fluid. As such, particular treatmentcomponents would be selected to filter the blood components from theCSF. For example, a membrane 258 with apertures sized to substantiallyprevent the flow of blood components, while large enough tosubstantially allow the entry of CSF as permeate, may be used.

As another example, if the method 400 is being used on a subjectsuffering from or suspected to be suffering from cyptococcal meningitis,the goal of the procedure may be to remove or inactivate Cryptococcusneoformans fungi that may be within the subject's CSF. The treatmentsite 112 may then be a lumen carrying CSF and treatment components maybe selected to heat the CSF to inactivate the fungi and then filter thefungi from the CSF.

The selecting and preparing the treatment site 112 step may includechoosing a particular treatment site 112. For example, a healthcareprofessional may select an individual who may benefit from havingtreatment performed on a bodily fluid and identify a reservoircontaining the fluid. This may include, as described above, a subjectsuffering from a cerebral vasospasm. Preparing the treatment site 112may include identifying an anatomical location for a procedure to accessthe treatment site 112 (for example, in a spinal portion 200, as shownin FIG. 2), sterilizing the location, or otherwise preparing thetreatment site 112 for the procedure. Selecting and preparing thetreatment site 112 may be performed according to the systems and methodsdescribed within this application or through other means. For example,selecting and preparing the treatment site 112 may be performedaccording to the various systems and methods described in U.S. patentapplication Ser. No. 14/743,652, which was previously incorporated byreference.

Installing tubing 114 may include connecting various components of thesystem 100. For example, retentate outlet 106 may be connected to flowregulator 118. This step may also include installing tubing 114 towithdraw fluid from and return fluid to the treatment site 112. Thisstep may include inserting a multi-lumen catheter into an anatomicallocation to place the treatment site 112 in fluid connection with thesystem 100 to enable fluid to be drawn into the intake 104 and returnedto the treatment site 112.

Calibrating components may include setting initial parameters for theuse of the system 100. This step may include establishing an initialflow rate, an initial pressure, and other initial parameters or systemsettings. The initial parameters may be based on observed or predictedclinical measures, including but not limited to an estimated amount offluid in the treatment site 112, the health of the subject, thepredicted ratio of retentate to permeate, and other factors.

Priming the system 100 may include adding a priming solution to one ormore of the components of the system 100. Depending on the configurationof the system 100, priming may be necessary for one or more componentsto function effectively. Depending on the treatment site 112, fluid, andthe subject, priming may be necessary to assure comfort or good health.In certain applications, the system 100 may be primed to enable thereturn of a volume of fluid while simultaneously withdrawing a volume offluid. This may be especially useful for applications where thetreatment site 112 has a relatively small volume of fluid (e.g., duringfiltration of CSF) or is otherwise sensitive to relative changes involume. Depending on the type of filtration being used, the length ofthe procedure, and other factors, priming fluid may be added during thefiltration procedure to make up for fluid lost during the procedure

At step 404, a volume of fluid is withdrawn from the treatment site 112.In certain circumstances, the fluid may be withdrawn using a pump ordevice located within the system 100. For example, the pump may be acomponent of one or more of the flow regulators 118; the treatmentsystem 102 (such as pump 222); and/or the combiner 116. The pump may beused to withdraw a volume of fluid from the treatment site 112.

In some embodiments, the rate at which the fluid is withdrawn from thetreatment site 112 is between approximately 0.01 mL/min andapproximately 100 mL/min, between approximately 0.04 mL/min andapproximately 30 mL/min, between approximately 0.1 mL/min andapproximately 10 mL/min, or in other ranges. However, the amountwithdrawn may be higher or lower depending on the application. Theamount may vary depending on various factors including but not limitedto the type of fluid being withdrawn, the viscosity of the fluid, theamount of fluid in the treatment site 112, and other factors. Theviscosity of the fluid may vary over time, and depending on theparticular subject. For example, the viscosity of CSF may be differentin a subject with meningitis than a subject with typical CSF. Once thefluid is withdrawn from the treatment site 112, the fluid may passthrough the tubing 114 and into the treatment system 102 via intake 104.

At step 406, the volume of fluid is treated. This may include the stepsof passing the fluid through the treatment unit 226 of the treatmentsystem 102. While the fluid passes through the treatment unit 226, itmay pass through multiple different components to treat the fluid. Forexample, the fluid may be heat treated using a heating unit and thenfiltered using a filtration unit. As another example, the fluid may passthrough various filtration components including but not limited totangential flow filtration, microfiltration, ultrafiltration,nanofiltration, dead-end filters, depth filters, and other filtrationdevices or mechanisms.

The treatment process may result in the separation of the fluid into aretentate flow and a permeate flow. The permeate flow may leave thetreatment system 102 through a permeate outlet 108 and the retentate mayleave the treatment system 102 through a retentate outlet 106. Dependingon the configuration of the filters and the goals of the method 400, insome implementations, the permeate may be the fluid to be returned tothe treatment site 112. In other implementations, the retentate may bereturned to the treatment site 112. The retentate may be a fluid thatcontains contaminants or is otherwise in a condition undesirable forreturning to the treatment site 112.

In certain embodiments the retentate may be successively orprogressively treated, such as by being treated again through anothertreatment process or by being treated again through the same treatmentsystem 102 by being redirected through it. For example, in someembodiments, the retentate may be passed through a flow regulator andinto treatment system 102 for additional filtration. The permeate mayflow from the permeate outlet 108 to a combiner for return to thetreatment site 112. The second retentate may be treated further. Oncethe fluid is sufficiently treated, the remaining retentate orcontaminants may be passed through a flow regulator and into a vessel110 for analysis, disposal, storage, or other use, or, alternatively, orin addition, the remaining retentate may be subjected to furtherprocessing, treatment, and/or filtration (any number of times), wherethe further treated fluid is, for example, directed to treatment site112, either directly or in combination with other fluids.

At step 408, characteristics of the fluid and/or the system may bemeasured. Measuring characteristics may include intermittent orcontinuous sampling and/or monitoring of characteristics or parametersof interest. While this step 408 is shown as occurring after thetreatment of the fluid 406, the step 408 may take place at any pointduring the process 400 where useful data may be gathered.

In certain embodiments, measuring characteristics may include measuringthe characteristics of the fluid withdrawn from the treatment site 112before, during, or after treatment. The characteristics measured mayinclude the presence or amount of particular contaminants, proteins,compounds, markers, and other fluid components present. As anotherexample, the ratio of permeate volume to retentate volume, the fluidflow rate from the treatment site 112, fluid temperature, fluid opacityor translucency or transparency, an absolute retentate flow rate, andthe rate of fluid flow to the treatment site 112 also may be measured.The performance characteristics of the system 100 may also be measured.For example, the efficiency of the treatment unit 226, the status of thetreatment unit 226 (for example, via the interface 210), and othermarkers of system 100 performance.

Data utilized by the system need not be limited to directly or actuallymeasured data. Data may be inferred from actually measured data. Forexample, retentate flow rate may be determined using a differencebetween a pump rate and a permeate rate. This method would allow thesystem to measure a value that may be unmeasurable, difficult tomeasure, or inaccurate due to, for example, changing viscosity.

In certain embodiments, the characteristics measured may includeinformation about a subject or input by a healthcare provider. Forexample, the system 100 may monitor the blood pressure, heart rate,stress, and other information of the subject. In addition toquantitative characteristics, qualitative measurements may be made aswell. For instance, subject discomfort and other qualities may bemeasured. These and other data may be measured by the sensor 224 and/orbe input into the system by an input device (for example, keyboard,touch screen, subject-monitoring device, and other devices for receivinginput) operably coupled to the system 100.

At step 410, a volume of fluid is returned to the treatment site 112. Incertain embodiments, the fluid is returned to the treatment site 112 assoon as fluid treatment has been completed. In certain embodiments, theflow rate of the fluid may be controlled. For example, a volume of fluidmay be buffered at the combiner 116 or in another area of the system 100for a time before being returned to the treatment site 112. Bufferingmay be used to smooth the return rate of the fluid, to allow time forthe fluid to reach a particular temperature, to allow time for aparticular additive to mix within the fluid, and for other reasons.

In certain embodiments, the rate and/or pressure at which the fluid isreturned to the treatment site 112 is controlled so that the fluid isreturned at such a rate or in such a manner as to maintain homeostasiswithin the treatment site 112. In certain embodiments, this may beaccomplished by returning fluid at the same rate at which fluid iscurrently being withdrawn from the system. In certain embodiments, thefluid may be returned at substantially the same flow rate at which itwas removed. The fluid volume removed from the system and returned tothe system may not be equal. This may be the case when removing asignificant quantity of contaminants from a treatment site. In certainembodiments, the difference may be made up through the addition of asecondary fluid or via the body's natural production.

In certain embodiments, a particular volume of additional fluid may bereturned to the treatment site 112. The additional fluid may be fluidthat was not withdrawn from the treatment site 112, previously withdrawnfrom the treatment site 112, withdrawn from a different treatment site,synthetically created, naturally created within the subject's body, oris otherwise different from the volume removed from the treatment site112 in step 404. The return of additional fluid may be used to, forexample, compensate for the volume of fluid that was filtered out,especially in circumstances where the treatment site 112 comprised onlya small amount of fluid at the start 402.

In certain embodiments, one or more therapeutic agents may be added tothe fluid prior to its return to the treatment site 112. The fluid maybe treated or mixed with a particular pharmacological agent. Forexample, when the fluid is CSF, the agent may be configured to bypassthe blood-brain barrier. The agents may include, but need not be limitedto, antibiotics, nerve growth factor, anti-inflammatory agents,pain-relief agents, agents designed to be delivered using intrathecalmeans, agents designed to affect a particular condition (e.g.,meningitis, Alzheimer's disease, depression, chronic pain, and otherconditions), and other agents.

As a specific example, the treatment site 112 may be a CSF-containingspace of a subject, such as the subarachnoid space or another spaceknown or thought to contain CSF. The space may only have a total ofapproximately 125 ml of CSF, and if the level drops below a certainthreshold (for example, approximately 85 ml), the subject may sufferundesirable side effects. If a particular large amount of the existingCSF comprises undesirable compounds, the volume of permeate may be smallenough to cause the fluid levels in the treatment site 112 to drop belowthe threshold. Consequently, the system 100 may return a volume ofadditional fluid (for example, artificial CSF or other suitable fluid)to adjust for the difference between the amount of withdrawn CSF beingreturned and the amount needed to be returned to maintain the volume ofthe treatment site 112 above the threshold amount.

In certain embodiments, the withdrawal and return of the fluid may occurin a pulsed manner. For example, the system 100 may withdraw aparticular volume and then cease withdrawing additional fluid. Thewithdrawn volume is treated and buffered (for example, at a combiner).An amount of the treated fluid from the buffer may be returned to thetreatment site 112 at about the same rate and/or for the about sametotal volume as a next volume is withdrawn from the treatment site 112.This process may allow the system to maintain treatment site 112 volumelevels relatively consistent and may be useful in circumstances wherethe processing time (for example, the time between the fluid beingwithdrawn from and returned to the treatment site 112) is long.

At step 412, a determination is made. The determination may be made by,for example, a healthcare professional, a processor system, or acombination thereof. For example, the healthcare professional mayanalyze the measured characteristics and come to a conclusion. Asanother example, the processing unit 208 may analyze the measuredcharacteristics using an algorithm or through other mechanisms. Thedetermination may be based on the measured parameters, a timer, aschedule, or other mechanisms. The determination may be used to changethe parameters of the system 100, may change over time, and may addressparticular measured characteristics.

For example, a determination may be made regarding the flow rate atwhich the fluid is being withdrawn and/or returned to the treatment site112. For example, it may be desirable to maintain substantially the samewithdrawal and return rate of the fluid. Specifically, if more fluid isbeing withdrawn from the treatment site 112 than is being returned, thenthe volume of fluid in the treatment site 112 may be decreasing overall.This may be undesirable because for certain fluids and certain treatmentsites 112, if the volume of the treatment site 112 passes a particularthreshold, undesirable side effects may occur. For instance, where thefluid being withdrawn is CSF, the flow rate may be such that the volumeof CSF removed from a human subject does not exceed about betweenapproximately 5 mL and approximately 20 mL over the course of one hour.That is, the volume of fluid does not decrease more than approximately 5mL to approximately 20 mL from its original starting volume in a onehour period of time. In certain embodiments, it may be desirable tomaintain an absolute retentate flow rate within a certain range ofacceptable retentate flow rates. In certain embodiments, the thresholdmay be between approximately 0.10 mL/min and approximately 0.30 mL/min.In certain embodiments, the threshold may be approximately 0.16 mL/min.In certain embodiments, the threshold may be between approximately 0.2mL/min and approximately 0.25 mL/min; however, other values may bedesirable in certain circumstances. In certain embodiments, a pump maybe running at approximately 1.0 mL/min and the retentate flow rate isapproximately 0.25 mL/min, the permeate flow rate is approximately 0.75mL/min, which is about a 3:1 ratio. However, if the pump speed wereincreased to approximately 2.0 mL/min, the retentate flow rate may beheld at approximately 0.25 mL/min, which leaves the permeate flow rateas approximately 1.75 mL/min, or about a 7:1 ratio. By maintaining theretentate flow rate within the threshold, the system may be consideringfunctioning as intended, despite the change in ratios.

Based on the measured characteristics, it may be determined that thebest way to address the disparity in the withdrawal and return rates maybe to decrease the flow rate to reduce the overall volume of fluid lostfrom the system. This may mean that, although there is a net loss offluid from the treatment site 112, the loss is occurring at a slowerrate. The rate may be sufficiently slow that, for example, that thesubject's body produces sufficient fluid to make up for the loss.

For example, at the beginning of the filtration process 400, the fluidmay contain large amounts of contaminants, resulting in a comparativelylarge amount of material being filtered out and a comparatively smallamount of the fluid being returned (for example, permeate). As thefiltration or treatment process continues, the amount of fluid beingtreated may decrease because the contaminants have already been filteredout (for example, retentate). In this scenario, a determination may bemade to begin the process at a relatively low flow rate and thenincrease it as the volume of the fluid being filtered out decreases. Inaddition, the determination may include altering the flow and/orpressure within the treatment unit 226 to achieve particular filteringresults.

As another example, the measured characteristics may be a subject'sexpressed discomfort. Withdrawing CSF from a CSF-containing space of asubject may cause symptoms of overdrainage, such as spinal headache.Symptoms of overdrainage may be able to be avoided or otherwiseaddressed by not withdrawing more than a threshold amount of CSF.However, the particular threshold may vary from subject to subject. Assuch, a predicted threshold may be different from an actual thresholdand the subject may experience symptoms sooner than expected. Inresponse to the subject expressing feelings of discomfort, thehealthcare professional may determine that the parameters of the processmay need to be changed.

In some embodiments, a system may predict the occurrence of a spinalheadache or a hemorrhage based on the amount of CSF removed from thesubject and/or the subject's intracranial pressure. The system may beconfigured to modify treatment parameters responsive to detecting that athreshold amount of CSF was removed or a threshold intracranial pressurewas reached. For example, the threshold amount may be an amount of CSFremoved, an amount of CSF removed over a period of time, or anintracranial pressure predicted to induce spinal headache. In someembodiments, the threshold amount of CSF removed or the threshold amountof CSF removed over a period of time, may be within about 100% to about50%, about 95%, about 90%, about 85%, or about 80% of the amountpredicted to cause a spinal headache. In some embodiments, the thresholdamount may be less than about 300% to about 100%, about 150%, about125%, about 110%, about 105%, or about 100% of the amount ofintracranial pressure predicted to cause a spinal headache. In someembodiments, the predicted volume of removed CSF (without replacement)that is sufficient to induce a spinal headache is an amount greater than15 milliliters per hour.

In certain embodiments, at step 412, the processing unit 228 and/or ahealthcare professional may determine that the process should becompleted. At this point, the flow diagram moves to end step 416. Incertain other embodiments, at step 412, the processing unit 228 and/or ahealthcare professional may determine that the process should continuesubstantially unchanged. Upon that determination, the flow diagram mayreturn to step 404. In still other embodiments, at step 412, theprocessing unit 228 and/or a healthcare professional may determine thatthe one or more parameters of the process should be changed. Upon thatdetermination, the flow diagram may move to step 414.

At step 414, one or more parameters of the system 100 are changed inresponse to a determination made in step 412. The parameters to bechanged may include inflow rate, outflow rate, buffer size, and otherparameters. Such parameters may be changed via, for example, theprocessing unit 206 sending a signal to the pump 222 or other componentof the system to modify the parameters. In certain embodiments, theparameters may be manually changed through input received at the input208. This may include parameters entered by a healthcare professional.In certain embodiments, parameters may be updated based on thedifference between the withdrawal volume and the returned volume (e.g.,a waste rate).

In certain embodiments, the updating parameters step 414 may includechanging the flow direction of the fluid. For example, a system mayinclude a plurality of treatment systems, which the fluid may bedirected to by the manipulation of a valve or other mechanisms forchanging fluid flow direction. Step 414 may include changing the fluidflow from one treatment system to a different treatment system. This maybe in response to determining that a second treatment system is moresuited for particular treatments than a first treatment system.

In certain embodiments, the updating parameters step 414 may includemodifying the positioning of the tubing at the treatment site 112. Forexample, one or more inflow or outflow tubes 114 may become clogged orotherwise be operating at a reduced capacity. In response, the tubing114 may be adjusted or otherwise modified to address the reducedcapacity issue. The healthcare professional may be alerted to the issueby a light, alarm or other indicia.

In certain embodiments, the updating parameters step 414 may includecleaning or otherwise modifying one or more components of the system100, such as the treatment unit 226. This may be accomplished by, forexample, changing back pressure and pump speed.

In certain embodiments, the updating parameters step 414 may includesensing characteristics of the system to determine whether the treatmentunit 226 or other components of the system are experiencing clogging.The sensed characteristic may include reading an alert state of thetreatment system or detecting an increase in filter pressure with nochange to system flow rates or other parameters of the system.Responsive to determining that there may be a clog in the system 100,the flow rate through the retentate port of the filters may beincreased. The increased flow rate may be the result of a user or thesystem opening a back pressure valve (e.g., a backpressure valve of theflow regulator 118). The opening of the valve may result in a surge offluid through one or more retentate ports of one or more filters into awaste collection area (e.g., vessel 110). The surge of fluid may resultin the flow returning to the treatment site 112 reducing to zero or evena negative rate. Thus, the operator or system controlling the flow ratemay take into account the volume of fluid lost and the possible effectson the patient as a result of this filter clearance mechanism.

At step 416, the process comes to an end. After the process iscompleted, various wind-up steps may be performed, including but notlimited to, applying a bandage to the subject, disassembling one or morecomponents of the system 100, analyzing an amount of the withdrawnfluid, analyzing the retentate, and other steps.

Increasing the Performance of Filtration Systems

In some embodiments, the performance of a filtration system, such astangential flow filtration systems, may be improved by heating the CSFto a target temperature, cooling the CSF to a target temperature,increasing CSF flow rate, applying light treatment to the CSF,separating cells via their dielectric properties, applying spiral and/orcentrifugal separation, binding additives to target particles, applyingcombinations thereof, or other techniques.

Heating or Cooling CSF to a Target Temperature

In some embodiments, heating or cooling CSF to a target temperature mayimprove performance of a filtration system and provide other beneficialresults. For example, heating or cooling CSF to a target temperature mayaffect microorganisms or other components of CSF. In particular, heatingor cooling the CSF may inhibit microorganisms within the CSF. Inhibitingmicroorganisms may include impairing the ability of the microorganism toreproduce, preventing the microorganism from being able to reproduce,killing the microorganism, inactivating the microorganisms, attenuatingthe microorganisms, or otherwise decreasing the potential negativeeffects of the microorganism. For a system or process to inhibitmicroorganisms, it need not inhibit all microorganisms. For example, thesystem may inhibit about 50%, about 60%, about 70%, about 80%, about90%, about 95%, about 99%, about 99.9%, about 99.99%, more than 99.99%,or another percentage of all microorganisms.

In addition to causing disease, microorganisms may reduce theeffectiveness of CSF treatment systems. Reproducing fungi, viruses,and/or bacteria may clog a filter or other parts of the treatment system100. Once a few microorganisms are on a filter, then they may continueto multiply and cover the entire filter. Further, once themicroorganisms become lodged in a portion of the system, that portionmay become a continuing reservoir of pathogens. One solution is to alterthe temperature of the CSF to kill or inhibit the microorganisms.

The target microorganism may be a fungus such as Cryptococcus neoformansor Cryptococcus gattii, fungi responsible for cryptococcal meningitis.C. neoformans thrives in environments that are warm, such as 37° C.,typical human body temperature. The ability of C. neoformans to thriveat this temperature makes it particularly deadly for people with immunecompromised systems. However, C. neoformans has a maximum growthtemperature of approximately 40° C. See, John R. Perfect, Cryptococcusneoformans: the Yeast that Likes It Hot, 6 FEMS YEAST RES 463-468(2006), hereby fully incorporated by reference for any and all purposesas if set forth herein in its entirety. See also, A. Madeira-Lopes, etal., Comparative study of the temperature profiles of growth and deathof the pathogenic yeast Cryptococcus neoformans and the non-pathogenicCryptococcus albidus, J. BASIC MICROBIOL. 26 (1986) 43-47, hereby fullyincorporated by reference for any and all purposes as if set forthherein in its entirety. Accordingly, heating CSF to a temperature of 40°C. or higher may kill or inhibit the growth of certain fungi, such as C.neoformans. Heating may be used to target other microorganisms orcomponents of CSF as well.

Like treating CSF with heat, cooling the CSF may impair thesurvivability of microorganisms. For example, cooling CSF may prevent orinhibit microorganisms from reproducing, thus reducing the likelihood ofthe microorganism clogging the treatment system 102 or otherwisereducing performance of the system 102. Some embodiments may beconfigured to cool CSF to a target temperature to precipitate outcertain proteins and/or slow or stop reproduction of a targetmicroorganism. The CSF may be cooled to a target temperature at which atarget protein precipitates out of the solution. Proteins precipitateout of a solution once the protein reaches a certain temperature. Inparticular, proteins may be soluble in solution but become folded solidas they are cooled. The temperature at which the protein precipitatesout may vary based on the target protein.

FIG. 7 illustrates systems and methods for withdrawing CSF, altering thetemperature of the CSF, filtering or otherwise conditioning the CSF, andreturning the CSF in a spinal region according some embodiments. Thesesystems and methods may be controlled and monitored by a processing unit228 and/or an interface 230. These components 228, 230 may be connectedto the other components of a treatment unit 102. The systems and methodsmay include the withdrawal and return of CSF from treatment sites 112using first ports 206 and second ports 208, respectively. The treatmentcycle may begin with the withdrawal of CSF from a lumbar cisterntreatment site 112 using the first port 206 and an elongate catheter204. The catheter 204 may be deployed such that the first port 206 islocated within the target lumbar cistern treatment site 112 and thesecond port 208 is located within a target mid-to-upper thoracictreatment site 112. The target lumbar cistern treatment site 112 may belocated in a region near or between the L2 and L4 vertebrae, in a regionnear or between the T12 and T10 vertebrae, or in other locations. Thetarget mid-to-upper thoracic treatment site 112 may be located in aregion near or between the T6 and T3 vertebrae, in a region near orbetween the T8 and T4 vertebrae between the C7 and T4 vertebrae, or inother locations though other locations may be used.

As the CSF is withdrawn from the target lumbar cistern treatment site112, the CSF passes through an inlet lumen of the catheter 204 andenters the treatment system 102 through the intake 104. Next, a sensor224 may read the pressure of the CSF as the CSF passes through a pump222 and an air trap 223. The pressure of the CSF is taken again using asensor 224 as the fluid moves through a temperature control unit 232.

The temperature control unit 232 may be a unit configured to cool orheat fluid as needed to reach a target temperature. The heating systemmay include various sensors and feedback loops to control thetemperature. Various cooling techniques may be used, including but notlimited to vapor-compression, thermoelectric cooling, radiator, coolbath, other techniques, or combinations thereof. Various heatingtechniques may be used, including but not limited to heating coils, warmbaths, other techniques, or combinations thereof. While the temperaturecontrol unit 232 is illustrated as located within the treatment system102, it may be located elsewhere within the system 100 as a whole. Forexample, the temperature control unit may be located external to thetreatment system 102. In some embodiments, the temperature control unit232 does not cool or warm the CSF directly and instead cools or warms aheat transfer fluid that is circulated to warm or cool the CSF. In otherembodiments, the temperature control unit 232 cools or warms a filter ofthe treatment unit 226 itself.

The temperature control unit 232 may modify the temperature of thewithdrawn CSF. For example, the temperature control unit 232 may cool orwarm the CSF. After the CSF leaves the temperature control unit 232 (oris otherwise cooled), the CSF may be filtered using a filter of thetreatment unit 226. In some embodiments, the CSF may be filtered beforeits temperature is modified. The treatment unit 226 may separate the CSFinto permeate and retentate. The retentate may pass through theretentate outlet 106 and deposited in a vessel 110 for disposal oradditional processing. The permeate may pass a pressure control sensor224 and a flow rate sensor 224. Next, the permeate passes through thepermeate outlet 108 and an outlet lumen of the catheter 204. Thepermeate then leaves the catheter 204 through the second port 208 and isdeposited in the cervicothoracic junction treatment site 112.

The heating or cooling of the CSF may, but need not, be rapid. Thesystem may be configured to alter the temperature of the CSF so the CSFreaches a target temperature by the time the CSF reaches a filter of thetreatment unit 226. The target temperature may be a temperature above orbelow a temperature which target microorganisms (or a percentagethereof) reproduce and/or survive. For example, the temperature may be atemperature above which about 50%, about 75%, about 90%, about 99%, orabout 99.9% of target microorganisms are unable to reproduce or survive.

The target temperature may also be a temperature below or above whichthe CSF is damaged or the proteins of the CSF are denatured. Forexample, albumin, which constitutes about 35% to about 80% of totalprotein in CSF, may be treated at 60° C. without being damaged.Ribonuclease (pH 2.0) may denature at about 30° C., ubiquitin (pH 4.0)may denature at about 82° C., and staphylococcal nuclease (pH 6.5) maydenature at about 38° C. See Cristiano L. Dias, et al., The hydrophobiceffect and its role in cold denaturation, 60 CRYOBIOLOGY 91-99 (2010),incorporated herein by reference for any and all purposes as if setforth herein in its entirety. In some embodiments, there may be anacceptable amount of denaturation of or damage to the CSF by heating.For example, the benefit to the subject by heating to the CSF to atarget temperature to kill a target microorganism may outweigh adetriment caused by denaturing some of the CSF's albumin. In someembodiments, the system may include a treatment system configured tocapture denatured proteins to reduce the amount of denatured proteinsreturning to the subject.

In some embodiments, the target temperature may be about 47° C. or about45° C. In some embodiments, the target temperature may be about 37° C.to about 90° C., about 40° C. to about 80° C., about 45° C. to about 65°C., about 45° C. to about 60° C., about 45° C. to about 55° C., or about50° C. In some embodiments, the target temperature may be a temperatureabove which a target microorganism reproduces and/or survives. Forexample, thermal death of C. neoformans begins at temperatures above 40°C. and increases rapidly as the temperature approaches 45° C.Accordingly, the temperature of the CSF may be increased within thisrange, or higher, to target C. neoformans. In some embodiments, thesystem may be configured to cool the CSF so the CSF reaches a targettemperature by the time the CSF reaches a filter of the treatment unit226. The target temperature may be a temperature below which a targetmicroorganism reproduces and/or survives. In some embodiments, thetarget temperature may be below about 37° C., below about 30° C., belowabout 20° C., and/or below about 10° C. The system 100 may be configuredto maintain the CSF at or near the target temperature for about 1 secondto about 10 seconds or about 5 seconds. Other time ranges may be used aswell. For example, about 1 second to about 10 minutes or about 5 secondsto about 5 minutes.

In some embodiments, the target may be a target protein that is thefirst or one of the first proteins to precipitate out of the CSF. Thisproperty of the target protein may enable it to be targeted forfiltration or special processing. For example, the target protein may beprecipitated out and then subject to special treatment (e.g.,filtration, disposal, or other treatments). In some embodiments, theprecipitated protein is added back to the solution.

In embodiments that warm the CSF, the system may be configured to allowthe CSF to cool to about 37° C. or cooler before it is returned to thesubject. In some embodiments, the CSF may cool quickly over shortlengths of tubing. For example, in approximately six inches of tubingCSF flowing at a rate of at approximately one milliliter a minute may becool from about 39° C. to about 22° C. In some embodiments, the tubingthrough which the treated CSF passes may be submerged in a cool bath tolower the temperature of the CSF. In other embodiments, the CSF may passthrough a radiator or other cooling system. In embodiments that cool theCSF, the cooled CSF may be warmed or be allowed to warm before returningto the subject. It may also be beneficial to maintain the CSF in acooled state as it is returned to the subject or otherwise cool thesubject. Such benefits and techniques are described in U.S. patentapplication Ser. No. 15/287,174, entitled “Devices and Methods forProviding Focal Cooling to the Brain and Spinal Cord”, which waspreviously incorporated by reference. These benefits include inducinghypothermia, which can have neuroprotective effects.

Applying Light Treatment to the CSF

Some embodiments may utilize light to treat CSF. For example,ultraviolet (UV) light may be applied to the CSF in order to treattargets. As another example, photodynamic therapy may be used to treattargets.

FIG. 8 illustrates systems and methods for treating CSF with UV lightaccording to some embodiments. The UV light treatment may be appliedextracorporeally or via a catheter disposed within the subject. Systemsand methods used to treat withdrawn CSF with UV light may be similar tothe systems and methods shown in FIG. 7 that change the temperature ofCSF. For example, in addition to or instead of the temperature controlunit 232, the treatment system 102 may include a UV treatment system500. The UV treatment system 500 may include a UV reactor 502, in whichCSF may flow from an intake 504 to an outlet 506. Disposed within the UVreactor 502 and within the flow path of the CSF is a UV lamp 508. The UVlamp 508 is configured to provide UV light within the UV reactor 502 totreat the CSF flowing therein. The particular wavelength of UV light maybe selected to improve the treatment qualities of the UV light. Inparticular, wavelengths in the range of about 270 nm to about 250 nm maybe used to effectively inactivate microorganisms. The UV lamp 508 may becontrolled by a control system 510. The control system 510 may includecomponents for controlling the operation of the UV lamp 508 and mayinteract with other components of the treatment system 102, such as theprocessing unit 228 and the interface 230. The system 500 may also beinclude various thermal insulation or UV shielding or other protectiveelements to avoid undesirable exposure to the UV radiation and to avoidundesirable heating of the CSF or components of the system 100 from theUV lamp. In some embodiments, the thermal insulation may be partially orentirely omitted so as to cause the heating of the CSF. This may be usedto cause heat treatment of the CSF, as previously described. Othersystems or methods of applying UV light may be used, including but notlimited to systems in which the UV lamp 508 is not disposed within aflow path of the CSF and is instead isolated from the flow of CSF.

The UV treatment system 500 may be configured to inactivate germs withinthe CSF. The dose of the UV treatment applied to the CSF may be afunction of the intensity of the UV light and the time over which the UVlight is applied to the CSF. For example, the dose may be described interms of millijoules per square centimeter. A dose may be selected toinactivate about 99.9% of microorganisms. Such a dose may vary dependingon the particular microorganism. See Gabriel Chevrefils, et al., UV DoseRequired to Achieve Incremental Log Inactivation of Bacteria, Protozoaand Viruses, IUVA NEWS, vol. 8, no. 1, p. 38-45 (March 2006),incorporated by reference herein for any and all purposes as if setforth herein in its entirety. For example, a UV dose to inactivatestaphylococcus may be in the range of about 3 mJ/cm² to about 8 mJ/cm².Typical doses to inactivate bacteria may be in the range of about 2mJ/cm² to about 16 mJ/cm². Typical doses to inactivate viruses may beabout 4 mJ/cm² to about 40 mJ/cm². The wavelength of the UV light may bein the about 400 nm to about 100 nm range. A dose may be selected toinactivate a smaller percentage of microorganism, such as about 50%,about 75%, about 90%, about 95%, or other percentages. A dose may beselected to achieve a particular log reduction in the number of livegerms, such as about a 1 log, 2 log, 3 log, 4 log, 5 log, 6 log, 7 log,or other log reduction. In some embodiments, reactor 502 may beconfigured such that CSF flowing through the reactor 502 may receive aparticular dose of light. This may be accomplished by, for example,lengthening or shortening the fluid flow path and/or increase ordecreasing the fluid flow speed of the CSF through the reactor 502.

In some embodiments, a method for treating the CSF with UV light mayinvolve withdrawing a volume of CSF, applying a germicidal dose of UVlight to the CSF, filtering the treated CSF, and returning the CSF tothe subject. Withdrawing and returning the CSF may be performedaccording to various methods and systems described herein.

In some embodiments, photodynamic therapy may be used to treat targets.Photodynamic therapy may involve activating photosensitive substanceswith light. See Renato Prates, et al., Photodynamic therapy can killCryptococcus neoformans in in vitro and in vivo models, PROC. OF SPIE,vol. 7165 (2009), incorporated by reference as if set forth herein inits entirety. The photosensitive substance may be a target within theCSF, such as a virus, bacteria, or fungi. In some embodiments, thephotosensitive substance may be an additive introduced into the CSF. Theadditive may bind to or otherwise interact with the target such thatwhen light is applied, the light and/or the additive ultimately causes achange in the target. For example, when the additive is exposed to aparticular frequency and/or intensity of light, the additive mayrelease, cause the release of, or accelerate the release of reactiveoxygen species (e.g., peroxides, super oxides, etc.). The reactiveoxygen species may inactive or otherwise damage the target. Variousadditives may be used. Some additives may include methylthioniniumchloride (methylene blue).

The systems and methods for applying photodynamic therapy may be similarto or the same as systems and methods for applying UV treatment. Forexample, photodynamic therapy may be applied using UV treatment system500 using the UV lamp 508 or a different light source. A light sourceused for photodynamic therapy may be a lamp, laser or another source ofelectromagnetic radiation. The light source for photodynamic therapy mayemit light at various wavelengths, including but not limited to awavelength selected from the range of about 10 nanometers to about 1millimeters. For example, the light source may be configured to emitlight at a frequency of 660 nanometers.

Increasing CSF Flow Rate or Flow Volume

In typical TFF systems, high fluid flow rate and fluid flow volume isused to prevent membrane clogging and improve TFF performance andlongevity. However, withdrawing fluid from and returning fluid to asubject at a high flow rate and high volumes presents challenges. Inparticular, should something go wrong with the system 100 (e.g., a clogor pinched tubing), high flow rates and high volumes may result in thesystem's problems quickly affecting the subject. For example, if CSF iswithdrawn and returned to the patient at a high rate and there is a clogin the system 100 that prevents the return of CSF to the patient, alarge amount of CSF may be withdrawn, causing problematically low levelsof CSF within the subject.

FIG. 9 illustrates an embodiment of a treatment system 102 having avalve 34 and feedback path 236 to artificially increase fluid flow rateacross the treatment unit 226, for example to improve the effectivenessof a TFF of the treatment unit 226. The valve 234 may control the amountof fluid flow heading towards the permeate outlet 108 and through afeedback path 236 towards the pump 222 from the treatment unit 226.Specifically, the valve 234 may restrict the amount of fluid flow backto the subject, thereby increasing the amount of fluid passing backthrough pump 222 and towards the treatment unit 226. The CSF that flowsback through the feedback path 236 through the pump 222 may be used toincrease the fluid flow rate across a filter. The processing unit 228may control the operation of the valve 234 to ensure that the amount offluid feeding back to the pump 222 is not too high. The total amount offluid within the feedback path 236 may be controlled, adjusted, orselected to ensure that the amount of fluid within the feedback path isbelow an amount that may negatively affect the subject (e.g., by causinga spinal headache in the subject).

In some embodiments, an array of micro-sized TFF systems may be usedwith a splitter. This system may be advantageous because the fluid flowrate may be faster through each of these TFF systems. Back pressure maybe controlled across each of the micro-sized TFF systems.

In some embodiments, another liquid (e.g., artificial CSF, saline, oranther liquid) may be added to boost the amount of fluid moving throughthe treatment unit 226 to increase performance. The additional volumewould enable additional fluid to pass through the treatment unit 226,thereby reducing the likelihood of the filter clogging.

In some embodiments, a volume of CSF may be removed from the patient,then no additional CSF is withdrawn or returned. The CSF isolated in thesystem 100 may then be filtered at a high speed without risk to thesubject. Following sufficient processing, the filtered CSF may bereturned and a next amount of CSF may be withdrawn.

Separating Cells Via their Dielectric Properties

Dielectrophoresis (DEP) is a technique in which a non-uniform electricfield is applied to dielectric particles, thereby causing the particlesto experience DEP forces. The way a particle responds to the non-uniformelectric field depends on the particle's unique dielectriccharacteristics, including permittivity, conductivity, and capacitance.DEP may be used to electrically separate cells, particles, or othercomponents of the CSF from each other or from the fluid itself. Thenon-uniform electric field that drives the particle movement andseparation can be generated in various ways, ranging from spatialdistortion of the field to different electrode configurations andgeometries.

One application of DEP forces is to particles in a fluid flowing througha chamber. By manipulating the forces acting on the particles (e.g., acombination of hydrodynamic lift, sedimentation, and dielectrophoreticforces) through DEP, a system can alter and control the location of theparticles in the fluid's velocity profile (speeding up or slowing down)and thus allow for separation from the rest of the fluid and removal ofthe particles. In addition, if multiple particles with differentdielectric properties are present in a fluid, it is possible to separatethem such that one type experiences positive DEP forces and the othertype experiences negative DEP forces.

FIG. 10 illustrates an example DEP system 600, which uses electrodes 602to create an electric field 604 to direct certain particles towards afirst path 606 or a second path 608. For example, first particles 610may be directed to toward the first path 606. Second particles 612 maybe directed toward the second path 608 or they may not be encouragedtoward a particular path at all.

Because dielectric properties of particles (e.g., dielectricconstant/permittivity, conductivity, and membrane capacitance) aredependent on size, structure, and composition, not only do cells havemeasureable dielectric properties, cells with different phenotypes havediffering dielectric properties. Thus, DEP may be used to separatecells, particles, or other biomarkers of interest from each other orfrom fluid.

Advantageously, DEP separation uses no physical filter and does not havean associated risk of clogging. Additionally, DEP allows for targetedseparation by targeting the unique inherent dielectric properties ofcells, and can therefore separate different cell types from each otherand selectively remove them.

In DEP, a non-uniform electric field is applied to a neutral or chargedparticle of interest to induce a force. The electric field may beinduced using either alternating current or direct current. Themagnitude and direction of force experienced by the particle depends onthe particle and medium's electrical properties, size, shape, structure,composition of particle, frequency of applied E field, applied voltage,etc. Thus, the force can be manipulated for the desired application.Both positive and negative dielectrophoretic forces (F_(DEP)) arepossible. A positive F_(DEP) means that the particle is attracted to thehigh-field regions (local E field maxima), and a negative DEP forcemeans that the particle is attracted to the low-field regions (local Efield minima). The determinant of whether the particle will experience apositive or a negative F_(DEP) is the polarizability of the particlecompared to the polarizability of the surrounding medium. If thepolarizability of the particle is higher than that of the surroundingmedium, it has more surface charges and will move toward the high fieldregion (positive DEP force). If the opposite is true, the surroundingfluid will move toward the high field region and the particle will bepushed to the low field region (negative DEP force). F_(DEP) is definedas

${\langle F_{DEP}\rangle} = {2\pi \; r^{3}\varepsilon_{m}{Re}\left\{ \frac{\varepsilon_{p}^{*} - \varepsilon_{m}^{*}}{\varepsilon_{p}^{*} + {2\varepsilon_{m}^{*}}} \right\} {\nabla{{\overset{\rightarrow}{E}}_{{rm}\; s}}^{2}}}$

where ∈_(m) and ∈_(p) represent the medium and particle permittivities,respectively, and the term in brackets represents the Claussus Mossotifactor, which represents the relative permittivities of the particlewith respect to the suspending medium. The permittivities are modelledas complex functions of the applied electric field, since the complexfunction allows for both a phase and magnitude (the causal behavior ofthe permittivity can be modeled as a phase difference), and the realpart of this term is used in the F_(DEP) calculation.

The non-uniform electric field can be generated by applying voltageacross electrodes of appropriate geometry or by placement of insulatorsbetween electrodes to spatially distort the electric field. Geometry ofelectrodes other than parallel plates may generate non-uniform electricfields, although some geometries are more common than others for bothdesign and efficiency purposes. The electrodes may be arranged in amicroelectrode array. The length of the microelectrode array may beselected to optimize separation yields.

DEP may involve the manipulation of forces applied to particles in afluid flowing through a column. A particle in a flowing fluidexperiences a combination of hydrodynamic lift and sedimentation forces,and by applying an external dielectrophoretic force perpendicular to theflow of the fluid, a system can control the position of a particle ofinterest in a fluid's velocity profile, thus causing it to speed up orslow down since particles at different positions in the fluid's velocityprofile travel at different velocities. The can facilitate separationand/or removal.

Differential dielectric affinity separation involves the separation oftwo different particle types by exploiting differences in the inherentdielectric properties of the two particles. An electric field may beapplied such that one of the particle types experiences a positiveF_(DEP) while the other experiences a negative, thus separating theparticles from each other.

Separation by differential dielectric affinity is affected by thefrequency of the applied electric field. When the DEP response isplotted as a function of applied electric field frequency, the crossoverfrequency is defined as the x-intercept (the frequency at which theF_(DEP)=0). When separating two different particles types, the systemmay be set to a frequency in between the crossover frequency of the twoparticles, such that one experiences a positive force and the otherexperiences a negative force.

The separation may cause a target type of particles to travel down atarget path. In some embodiments, the target path may be through aporous membrane (e.g., membrane 258) on the sides of a fluid pathway. Inparticular, the target molecule may be attracted to an electrode on theother side of the membrane. The target particle may be pass through thefilter. Once the target particle passes through the membrane, it may beprevented or discouraged from returning to the other side of themembrane.

In some embodiments, the target path may be a particular path at anintersection. For example, there may be a Y-junction in a flow path. Thetarget particles may be pulled in a particular direction, so they aremore likely to flow in one direction over another. This filtration maybe a statistical process and be performed several times so there is aparticular level of filtration (e.g., 99.9% filtration). In thisprocess, there may be separate side loops that work through theseparated material at a high rate. In some embodiments, there may bemore than two potential flow paths. For example, there may be threedifferent flow paths at a particular junction. The different flow pathsmay be separated based on the target molecule. In some embodiments, theparticular flow paths may be subjected to different levels of treatment.

Many diseases of the central nervous system manifest in the CSF and showCSF dissemination of certain foreign/unwanted matter such as cells,proteins, or other molecules. It would be advantageous to have a methodto specifically target and separate these particles from each other orfrom the fluid itself based on their inherent dielectriccharacteristics. Some embodiments may be directed to a method ofelectrical separation that allows for the application of CSFtherapeutics to a wider range of central nervous system disease states(other than subarachnoid hemorrhage-induced cerebral vasospasm) thatallows for specific targeting and removal without the use of a physicalfilter.

Examples of targets include leptomeningeal carcinomatosis tumor cells,which may be present in the CSF and resulting from metastases of variouscancers. Similarly, glioblastoma, a rapidly-progressing and usuallyfatal tumor that generally forms in the central hemispheres of the brainand arises from astrocytes, tumor cells may disseminate in the CSF. CSFdissemination occurs in 10-27% of cases of glioblastoma patients. See,e.g., Cerebral Glioblastoma with Cerebrospinal Fluid Dissemination,NEUROSURGERY, vol. 25, issue 4, pp. 533-540 (October 1989), hereby fullyincorporated by reference for any and all purposes as if set forthherein in its entirety. The circulation of tumor cells in the CSFpathways can lead to blockages, hydrocephalus, and further spread ofcancer. In addition, Cryptoccocal meningitis, Alzheimer's, MultipleSclerosis, and a variety of other central nervous system disease statesare associated with CSF biomarkers that are not present in normal CSF.These biomarkers are correlated to the pathology and progression ofthese diseases. Examples of CSF biomarkers associated with these diseasestates include fungi, p-tau proteins (hyperphosphorylated tau proteins),B-amyloid deposits, cytokines, B/T cells, autoantibodies, and more.Different proteins may have different dielectric properties. See Jed W.Pitera, et al., Dielectric Properties of Proteins from Simulation: TheEffects of Solvent, Ligands, pH, and Temperature, BIOPHYSICAL JOURNAL80, no. 6 (June 2001): 2546-55. doi:10.1016/S0006-3495(01)76226-1,hereby fully incorporated by reference for any and all purposes as ifset forth herein in its entirety. Therefore, DEP-based filtration may beused to target biomarkers associated with a variety of disease states.

Many DEP research studies perform separation experiments in a series ofdiscontinuous steps involving a loading of the suspension step, awashing step, and an elution step. Such discontinuous procedures limitthe separation throughput and scaling of the technique and would makeintegration of the DEP separator with a CSF treatment system difficult.Thus it may be desirable to implement a continuous system. See Ki-HoHan, et al., Lateral-Driven Continuous Dielectrophoretic Microseparatorsfor Blood Cells Suspended in a Highly Conductive Medium, LAB ON A CHIP8, no. 7 (Jun. 27, 2008): 1079-86. doi:10.1039/B802321B, hereby fullyincorporated by reference for any and all purposes as if set forthherein in its entirety.

The medium in which the target is located is also a factor in applyingDEP to CSF. The relative polarizability (which depends on permittivityand conductivity) of the particle with respect to the medium determineswhether a particle will experience a positive or negative F_(DEP). Aparticle that is more polarizable than the surrounding medium willexperience a positive DEP force, and vice versa. Most DEP separationstudies control the conductivity of the suspension medium to ensure alow conductivity (compared to physiological medium) of about 30-60 mS/m,to optimize parameters for strong positive DEP separation forces.However, controlling the conductivity of the medium is not clinicallyrelevant and a low conductivity suspension medium is not physiologicallyrelevant since physiological fluids usually have higher conductivities(10-100 times higher than mediums used in many DEP experiments). Theelectrical conductivity of the CSF at body temperature may beapproximately 1790 mS/m, which is about two orders of magnitude higherthan the conductivity of mediums used in many DEP research studies.Stephen B. Baumann, et al., The Electrical Conductivity of HumanCerebrospinal Fluid at Body Temperature, IEEE TRANSACTIONS ON BIOMEDICALENGINEERING 44, no. 3 (March 1997): 220-23. doi:10.1109/10.554770,hereby fully incorporated by reference for any and all purposes as ifset forth herein in its entirety.

Most cells in CSF would experience negative DEP forces at a wide rangeof E field frequencies, because CSF is a highly conductive suspensionmedium. Ki-Ho Han, et al., Lateral-Driven Continuous DielectrophoreticMicroseparators for Blood Cells Suspended in a Highly Conductive Medium,LAB ON A CHIP 8, no. 7 (Jun. 27, 2008): 1079-86. doi:10.1039/B802321B,hereby fully incorporated by reference for any and all purposes as ifset forth herein in its entirety. This presents a challenge for trappingand removing particles, but electrode channel design may be used toaddress this challenge. Studies have used electrodes of polynomialgeometry constructed using photolithography for directing and collectingyeast cells away from electrode edges. Y. Huang, et al., ElectrodeDesign for Negative Dielectrophoresis, MEASUREMENT SCIENCE ANDTECHNOLOGY 2, no. 12 (Dec. 1, 1991): 1142-46.doi:10.1088/0957-0233/2/12/005, hereby fully incorporated by referencefor any and all purposes as if set forth herein in its entirety.Potential application of this system would be trapping or suspending thecells of interest in a certain area and then washing them away via aseparate flow loop or channel. FIGS. 11 and 12 illustrate embodiments ofpolynomial channel paths, with single and double dash marks on pathsindicating differences in electrical polarity on a given curve.

DEP separators may be scaled to handle larger volumes of fluid; however,many DEP separators used in research studies are limited tomicrofluidics applications with low throughput. The main reason for thisis that electric field intensity decays exponentially with increasingdistance from electrodes, and F_(DEP) is proportional to the electricfield intensity. Studies using planar microelectrode arrays, whichusually lie at the bottom of the chamber, are limited in column heightand thus volume of fluid they can process because the E field isinversely proportional to the square of the distance from electrodes; aparticle in the fluid towards top of chamber (farther away from theelectrodes) may not be exposed to the E field, or may not be exposed toenough E field for it to experience an appreciable force necessary forseparation.

A potential solution to this is the use of 3D microelectrode array (MEA)designs. As opposed to a planar microelectrode array resting on thebottom of the column, 3D MEAs would extend the E field further up intofluid, allowing particles in all locations of the fluid's velocityprofile to experience an appreciable dielectrophoretic force. 3Dmicroelectrodes may affect the fluid's velocity profile. The fluid'svelocity profile can be modeled using Navier-Stokes equations andfinite-element analysis.

Studies have proposed the use of carbon microfabrication techniques tocorrelate the electric field distribution with the velocity profile ofthe fluid. Benjamin Y. Park, et al., 3-D Electrode Designs forFlow-through Dielectrophoretic Systems, ELECTROPHORESIS 26, no. 19(October 2005): 3745-57. doi:10.1002/elps.200500138, hereby fullyincorporated by reference for any and all purposes as if set forthherein in its entirety. In some embodiments, if a particle experiencesnegative DEP force under the experimental conditions, it will beattracted to low field regions, thus it may be advantageous to havehigher flow rates in these regions to promote separation and removal.Accordingly, the electrode geometry may be designed such that low fieldregions coincide with high velocity regions in the fluid's velocityprofile.

Options for 3D electrode design include extensions of 2D designs, orother designs. FIGS. 13-15 illustrate some example designs. Benjamin Y.Park, et al., 3-D Electrode Designs for Flow-through DielectrophoreticSystems, ELECTROPHORESIS 26, no. 19 (October 2005): 3745-57.doi:10.1002/elps.200500138, hereby fully incorporated by reference forany and all purposes as if set forth herein in its entirety. FIG. 13illustrates a DEP system 600 having 3D cylindrical electrodes 602 havinga diameter of 10 μm, a center to center distance of 20 μm. Voltages of+/−1V may be applied to the electrodes 602, with the voltage on eachelectrode 602 is opposite in polarity to the adjacent electrodes). FIG.14 illustrates a DEP system 600 having 3D castellated electrodes 602having a length of, 5 μm. Voltages of +/−5V may be applied to theelectrodes. The voltage on each electrode 602 may be opposite inpolarity to the adjacent electrodes 602. FIG. 15 illustrates a DEPsystem 600 having 3D semi-circular electrode design with long, semicylindrical electrodes 602 places near each other. The electrodes 602may be approximately 400 μm in diameter with 100 μm distance betweenelectrodes 602. Voltages of +/−5V may be applied to the electrodes. Insome embodiments, there may be closely-spaced wire electrodes being 1.58mm in diameter, and having spacing between electrodes of about 250 μmwith a channel that is approximately 2 mm in height). In someembodiments, multiple arrays of electrodes can be stacked for increasedthroughput. In addition, it is also possible to line both the top andbottom of the chamber with microelectrodes, thus creating a pairedmicroelectrode multi-layered structure within the microchannel. D. Chen,et al., A 3D Paired Microelectrode Array for Accumulation and Separationof Microparticles, J. OF MICROMECHANICS AND MICROENGINEERING 16, no. 7(Jul. 1, 2006): 1162. doi:10.1088/0960-1317/16/7/008, hereby fullyincorporated by reference for any and all purposes as if set forthherein in its entirety. For example, this design may generatedielectrophoretic gates between the top and bottom electrodes withhigh-frequency AC voltage. Variables such as channel height, particlesize and dielectric characteristics, electrode width and spacing, andmore determine whether the particle settles near the gates or penetratethe gates.

A potential advantage of electrical separation is that since there is nouse of a physical filter, there is reduced risk of clogging and thefiltration is not limited by the size of the particles of interest. Forexample, consider a situation in which it was desirable to separate twoparticles of the same size/mass from each other, or if multipleparticles of the same size/mass were present in the fluid and it wasdesirable to only remove one type of particle from the fluid. In eitherof these cases, electrical separation could be an option forpurification since size/mass-based filtration would not be applicable.

Because DEP exploits inherent dielectric characteristic differencesbetween cells of differing phenotypes, it has the potential to bebroadly applicable to a range of central nervous system disease states.

There may be challenges associated with this technique. For example,electrode surfaces may become saturated with cells after a period oftime (e.g., approximately 30 minutes). In general, if the concentrationof the target particle in the fluid is too high, the electrode surfacesand/or areas where particles are being collected may become saturatedafter a certain period of time. This would result in a decrease inseparation efficiency and cells would cease being separated from thefluid (e.g., CSF would mostly likely just continue being circulated asopposed to circulated and purified). Thus, the concentration of thetarget molecule in the CSF may be a consideration.

In some embodiments, a method for treating the CSF with dielectricseparation may involve withdrawing a volume of CSF and encouragingtarget molecules to flow in a particular direction or along a specificpath by inducing an electric field through the CSF. Withdrawing the CSFmay be performed according to various methods and systems describedherein.

In some embodiments, a method for treating the CSF with dielectricseparation may involve withdrawing a volume of CSF, capturing targetmolecules (e.g., at electrode surfaces or in collection wells) byapplying an electric field to the CSF, and returning the processed CSFto the subject.

Applying Spiral and/or Centrifugal Separation

FIG. 16 illustrates systems and methods for using spiral and/orcentrifugal separation (with or without recombination) by mass separatetargets from CSF, including a centrifugal separation system 700. Inparticular, the system 700 may include a path 702 connecting an intake704 to a first outlet 706 and a second outlet 708. The path 702 followsa spiral pattern from the intake 704 to the first and second outlets706, 708. FIG. 17 illustrates a cross section of the path 702. The pathmay have a trapezoidal cross section. As first particles 710 and secondparticles 712 travel through the path 702, centrifugal forces impartedon the particles 710, 712 by the spiral path may cause heavier particles(e.g., first particles 710) to gather at one end of the cross sectionand lighter particles to gather at the opposite end of the crosssection. The fork that leads to the first and second outlets 706, 708may be configured to use this tendency to gather to separate theparticles, such that the first particles 710 generally travel toward thefirst outlet 706 and the second particles 712 generally travel towardsthe second outlet 708. In embodiments where the targets are separated bymass, some molecules may be recombined and others may be excluded so asto function as a notch or bandpass filter in the mass. In someembodiments, a hydrocyclone may be used. A hydrocyclone may applycentrifugal force to the CSF encouraging the separation of components ofthe CSF based on their mass.

In some embodiments, a method for applying spiral and/or centrifugalseparation may include withdrawing a volume of CSF, passing the volumeof CSF through a hydrocyclone to separate the CSF into first and secondvolumes, and returning one of the first or second volumes to thesubject. Withdrawing and returning the CSF may be performed according tovarious methods and systems described herein.

Binding Additives to Target Molecules

Some systems and methods may involve introducing an additive into theCSF. This step may include directly introducing the additive into thetreatment site 112 (e.g., via port 124) or by other means (e.g., such asan orally-administered substance). In some embodiments, the additive isadded to the CSF after the CSF has been removed from the treatment site112. The additive may serve various purposes, including but not limitedto improving the effectiveness of the treatment system 102 (e.g., bymaking a material more easily filtered-out by a filter of the treatmentsystem 102), increasing the safety of the procedure, improving thehealth of the patient, or other purposes. For example, in certainembodiments, the additive may be a binding drug, molecule, salt, orother binding material. The binding additive may preferentially bind tocertain target materials within the CSF to modify how the materialinteracts with the treatment system 102.

For example, in certain embodiments, the binding additive maypreferentially bind to a target material (e.g., a protein or cytokine),causing the target to become larger in size or precipitate out, therebymaking the target more easily removed by a filter of the treatmentsystem 102. In certain embodiments, the additive may be configured tochange a dielectric property of the target to make the target more orless easily filtered by a filter of the treatment system 102. In certainembodiments, the additive is given a particular amount of time to workor otherwise interact with target before a next step is taken. Forexample, there may be a waiting period after the additive has beenintroduced to the CSF to give the additive time to bind with orotherwise modify the target before the CSF is filtered or otherwiseprocessed.

In some embodiments, an additive has specific properties (e.g., size,mass, dielectric constant, magnetism, etc.), which may be used to targetparticular targets (e.g., by chemically or biologically targeting aprotein or some other tag). The additive molecules may attach to thetarget particle, so the target particle is more easily separable fromthe CSF. For example, the additive molecule may make the particle ofinterest larger so the additive-target combination may be more easilyseparated by size-exclusion filtration. The additive-target combinationmay be heavier to encourage separation by centrifugal filtration (e.g.,as described above). The additive-target combination may have altereddielectric properties, making it more easily separable using thedielectric separation method.

As a particular example, a health care professional may desire to aremove a target protein, and introduce a gold micro or nano particleadditive to the CSF. The additive may have a tag (e.g., a chemical tag)for the target. The additive may then attach to the target, making theadditive-target combination larger or otherwise more easily filtered.The now-larger additive-target combination is then more easily removed.

In some embodiments, a treatment system 102 may include a pre-mixingsystem in which the additive is mixed with the CSF. The pre-mixingsystem may be configured to cause the additive to mix with the CSF andreact with the target. The pre-mixing system may be configured withparticular parameters, such as a particular temperature, pressure, orother conditions. The pre-mixing system may be configured such that theadditive is allowed to react with the target for a particular amount oftime before the CSF leaves the system. The additive-target combinationmay then move through the system and eventually be filtered out (e.g.,using a dead end filter).

In some embodiments, the separated additive-target combination isdeposited into a waste bag. The additive-target combination may beseparated from the CSF in the waste bag (e.g., because theadditive-target combination sank to the bottom of the waste bag) and theCSF in the waste bag may be recycled into the system 100. For example,the CSF may be added back to an inflow of the treatment system 102 andprocessed again.

In some embodiments, the additive includes magnetic nanobeads configuredto capture particular molecules, pathogens, germs, toxins, or othertargets. For example, the magnetic nanobeads may be coated withengineered human opsonin (mannose-binding lectin), which may capture awide variety of targets. Once the additive binds to the target, theadditive-target combination may be separated from the CSF using amagnet.

Combined Systems

In some embodiments, there may be multiple divided subloops (in parallelor series) that have different treatments and are recombined asnecessary. The different loops may enable different treatment. Forexample, one loop may be con figured to use UV light to kill bacteriaand then the fluid passes through a different subloop configured to heatthe fluid to slow reproduction of fungus and then cooling the CSF beforeit is returned to the subject. In some embodiments, vibrating thetreatment unit 226 may discourage clogging, coagulating, clotting, andsettling on the treatment unit 226.

Multiple systems may be used to provide incremental enhancements to theCSF prior to filtration. For example, filtering using a hydrocyclone anddielectric separation techniques may remove a percentage of the targetmolecules, with the remaining amount removed by a TFF system. While notnecessarily removing the need for a filtering system, the hydrocycloneand dielectric separation may remove an amount of target (or other)particles to improve performance of a treatment system.

Targets

The targets may be any kind of biomarker, the removal of which is or maybe associated with particular health outcomes for the subject. In someembodiments, the target may be an organism known to or thought to causea particular disease or health condition, such as meningitis. In someembodiments, the targets may be metastases. In some embodiments, thetarget may be polysaccharide capsules. For example, some germs, such asCryptococcus and Neisseria meningitides, are encapsulated in apolysaccharide capsule. After the germ sheds the capsule, the capsulemay be suspended within the CSF. Both the germ and the capsule may betargeted for removal. While the germ may be a primary target, thecapsule is relatively large and may problematically cause clogging insome filters. As another example, glial fibrillary acid proteins may betargeted. These proteins may be a marker for astrocytic differentiationin patients with cerebral glioblastoma. Other markers of CSFdissemination of glioblastoma may also be removed.

There are a number of cytokines that have been implicated ininflammation in acute brain injury and chronic brain injury, which mayalso be a target. Similar to other disease processes, the early stage ofinflammation can facilitate healing but inflammation that increases overtime and becomes “chronic” can have severe long-term effects oncognition and overall mental health.

Embodiments may enable filtration of cytokines like TNF-a, interleukinsand other cytokines from the CSF of a compromised brain. By activelydecreasing the cytokine load, during a chronic inflammation, overallbrain health would improve significantly. Removal of substances in the25 kDa to 80 kDA range would be important to protect on the filtrationside.

Examples of cytokines and other proteins that may be targeted mayinclude, but need to be limited to, EGF, Eotaxin, E-selectin, fasligand, FGF2, Flt3 lig, fractalkine, G-CSF, GM-CSF, GRO, ICAM, IFNa2,IFNg, IL10, IL12p40, IL12p70, IL13, IL15, IL17, IL1a, IL1b, IL1ra, IL2,IL3, IL4, IL5, IL6, IL7, IL8, IL9, integrins, IP10, L-selectin, MCP1,MCP3, MDC, MIP1a, MIP1b, PDGF-AA, PDGF-AAAB, P-selectin, RANTES, sCD40L,sIL2R, TGFa, TNF, TNFb, VCAM, VEGF, and others. In some embodiments, thetreatment unit 226 may be configured to capture and absorb cytokines inthe about 10 to about 50 kDa range where most cytokines reside.

Various journal articles and other publications are cited in thisdisclosure. Each of those is hereby incorporated by reference herein forany and all purposes, as if fully set forth herein.

Within this disclosure, connection references (for example, attached,coupled, connected, and joined) may include intermediate members betweena collection of components and relative movement between components.Such references do not necessarily infer that two components aredirectly connected and in fixed relation to each other. The exemplarydrawings are for purposes of illustration only and the dimensions,positions, order and relative sizes reflected in the drawings attachedhereto may vary.

The above specification provides a complete description of the structureand use of exemplary embodiments as claimed below. Although variousembodiments of the invention as claimed have been described above with acertain degree of particularity, or with reference to one or moreindividual embodiments, those skilled in the art could make numerousalterations to the disclosed embodiments without departing from thespirit or scope of this disclosure. Other embodiments are thereforecontemplated. It is intended that all matter contained in the abovedescription and shown in the accompanying drawings shall be interpretedas illustrative only of particular embodiments and not limiting. Changesin detail or structure may be made without departing from the basicelements of the disclosure as defined in the following claims.

What is claimed is:
 1. A method for treating cerebrospinal fluid (CSF)of a human or animal subject, the method comprising the steps of:withdrawing a volume of fluid comprising CSF from a CSF-containing spaceof the subject at a first flow rate; treating the volume of fluid;measuring a characteristic of the volume of fluid using a sensor;returning at least a portion of the treated volume of fluid to theCSF-containing space of the subject at a second flow rate; and updatinga parameter of a set of operation parameters based on the measuredcharacteristic responsive to determining that the measuredcharacteristic passes a predetermined threshold.
 2. The method of claim1, wherein treating the volume of fluid comprises filtering the volumeof fluid into permeate and retentate using a tangential flow filter. 3.The method of claim 2, further comprising increasing a rate at which thevolume of fluid passes through the tangential flow filter by diverting aportion of the permeate or retentate back through the tangential flowfilter.
 4. The method of claim 2, further comprising inhibitingmicroorganism growth on the tangential flow filter by heating of thefilter.
 5. The method of claim 1, wherein treating the volume of fluidcomprises separating a first portion of the volume of fluid from asecond portion of the volume of fluid by applying a non-uniform electricfield to the volume of fluid.
 6. The method of claim 1, wherein treatingthe volume of fluid comprises separating a first portion of the volumeof fluid from a second portion of the volume of fluid by passing thevolume of fluid through a hydrocyclone.
 7. The method of claim 1,wherein treating the volume of fluid comprises inactivating a targetmicroorganism by heating or cooling the volume of fluid to a targettemperature.
 8. The method of claim 7, wherein the target microorganismis C. neoformans or C. gattii and the target temperature is betweenapproximately 40° C. and approximately 45° C.
 9. The method of claim 1,wherein treating the volume of fluid comprises inactivating a targetmicroorganism by applying a dose of ultraviolet radiation to the volumeof fluid.
 10. The method of claim 9, wherein the microorganism is anorganism known or thought to cause meningitis and the dose is about 5mJ/cm² to about 8 mJ/cm².
 11. The method of claim 9, wherein theultraviolet radiation has a wavelength of about 400 nm to about 100 nm.12. The method of claim 1, further comprising introducing an additive tothe volume of fluid, the additive configured to improve theeffectiveness of treating the volume of fluid.
 13. The method of claim12, wherein the additive is a gold micro or nano particle.
 14. Themethod of claim 12, wherein the additive is configured to preferentiallybind to a target material within the volume of fluid to modify how thematerial is treated.
 15. The method of claim 14, wherein the treatmentincludes filtration of the volume of CSF; and wherein the additive isconfigured to improve the effectiveness of the treatment step by bindingto the target material to cause the target material to be more easilyfiltered by the filter.
 16. The method of claim 1, wherein treating thevolume of fluid comprises targeting a predetermined target.
 17. Themethod of claim 16, wherein the target is a protein selected from agroup consisting of EGF, Eotaxin, E-selectin, fas ligand, FGF2, Flt3lig, fractalkine, G-CSF, GM-CSF, GRO, ICAM, IFNa2, IFNg, IL10, IL12p40,IL12p70, IL13, IL15, IL17, IL1a, IL1b, IL1ra, IL2, IL3, IL4, IL5, IL6,IL7, IL8, IL9, integrins, IP10, L-selectin, MCP1, MCP3, MDC, MIP1a,MIP1b, PDGF-AA, PDGF-AAAB, P-selectin, RANTES, sCD40L, sIL2R, TGFa, TNF,TNFb, VCAM, and VEGF.
 18. The method of claim 16, wherein the target isa polysaccharide capsule.
 19. The method of claim 1 wherein thethreshold is a volume of removed CSF that is sufficient to induce aspinal headache, or a level of intracranial pressure sufficient toinduce a spinal headache or a hemorrhage.
 20. The method of claim 1,wherein treating the volume of fluid comprises one or more of: filteringthe volume of fluid into permeate and retentate using a tangential flowfilter; separating a first portion of the volume of fluid from a secondportion of the volume of fluid by applying a non-uniform electric fieldto the volume of fluid; and separating a first portion of the volume offluid from a second portion of the volume of fluid by passing the volumeof fluid through a hydrocyclone; and wherein treating the volume offluid further comprises one or more of inactivating a targetmicroorganism by heating or cooling the volume of fluid to a targettemperature; and inactivating a target microorganism by applying a doseof ultraviolet radiation to the volume of fluid.